Measurement apparatus, information processing apparatus, and non-transitory computer readable medium

ABSTRACT

A measurement apparatus includes a light irradiator, a light receiver, and a processor. The light irradiator is able to apply light from multiple directions to a specific portion of a subject to be measured. The light receiver receives light reflected by the specific portion. The processor is configured to: cause the light irradiator to apply light to the specific portion sequentially from the multiple directions; and acquire information concerning a tilt of a surface of the specific portion, based on information on light received by the light receiver when light is applied to the specific portion from a first direction and information on light received by the light receiver when light is applied to the specific portion from a second direction. The multiple directions include the first and second directions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2020-058149 filed Mar. 27, 2020.

BACKGROUND (i) Technical Field

The present disclosure relates to a measurement apparatus, aninformation processing apparatus, and a non-transitory computer readablemedium.

(ii) Related Art

Japanese Unexamined Patent Application Publication No. 2014-240830discloses the following processing. The scanning distance of a linelight source is set in accordance with the characteristics of a subjectto be measured. The movement of the line light source and the imaging ofan imager are controlled. Reflection characteristics of the subject areestimated from multiple images of the subject captured by the imager.

Japanese Unexamined Patent Application Publication No. 2017-134561discloses the following device. The device includes a memory, aluminance information obtainer, a selector, and a normal line estimator.In the memory, multiple reflection characteristics models are stored.The luminance information obtainer obtains luminance informationconcerning a subject from multiple images captured from the subject. Theselector selects a specific model from among the multiple reflectioncharacteristics models, based on the obtained luminance information. Thenormal line estimator obtains normal line information by using thespecific model and variations in the luminance information according tothe light source conditions.

SUMMARY

To determine how much the surface of a specific portion of a subject istilted, the following procedure may be taken. Light is applied to thespecific portion from one direction, and light reflected by the specificportion is received by a light receiver. Then, based on the intensity ofthe reflected light, a tilt of the surface of the specific portion isdetermined.

The intensity of reflected light received by the light receiver issusceptible to the color of the specific portion. That is, the intensityof reflected light varies in accordance with the color of the specificportion. This may fail to accurately determine how much the surface ofthe specific portion is tilted.

Aspects of non-limiting embodiments of the present disclosure relate tomaking it possible to determine with higher accuracy how much thesurface of a specific portion of a subject is tilted, compared with whensuch a determination is made by applying light to the specific portiononly from one direction.

Aspects of certain non-limiting embodiments of the present disclosureaddress the above advantages and/or other advantages not describedabove. However, aspects of the non-limiting embodiments are not requiredto address the advantages described above, and aspects of thenon-limiting embodiments of the present disclosure may not addressadvantages described above.

According to an aspect of the present disclosure, there is provided ameasurement apparatus including a light irradiator, a light receiver,and a processor. The light irradiator is able to apply light frommultiple directions to a specific portion of a subject to be measured.The light receiver receives light reflected by the specific portion. Theprocessor is configured to: cause the light irradiator to apply light tothe specific portion sequentially from the multiple directions; andacquire information concerning a tilt of a surface of the specificportion, based on information on light received by the light receiverwhen light is applied to the specific portion from a first direction andinformation on light received by the light receiver when light isapplied to the specific portion from a second direction. The multipledirections include the first and second directions.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present disclosure will be described indetail based on the following figures, wherein:

FIG. 1 illustrates the overall configuration of an image readingapparatus;

FIG. 2 is a block diagram illustrating the configuration of acontroller;

FIG. 3 illustrates the configuration of a reading unit and otherelements;

FIGS. 4A and 4B illustrate the states of the reading unit and otherelements;

FIG. 5 illustrates the relationship between the angle of incidence andthe angle of a normal line;

FIG. 6 illustrates a sensor, first and second light sources, and aspecific portion of a subject, as viewed from the direction indicated bythe arrow VI in FIG. 3;

FIGS. 7A and 7B illustrate the sensor, the first and second lightsources, and a specific portion of a subject, as viewed from thedirection indicated by the arrow VII in FIG. 3;

FIG. 8 illustrates a subject as viewed from the direction indicated bythe arrow VIII in FIG. 3;

FIG. 9 illustrates the first, second, and third light sources and thesensor as viewed from the direction indicated by the arrow IX in FIG. 3;

FIG. 10 illustrates another example of the configuration of the readingunit;

FIG. 11 illustrates the first and second light sources and a specificportion of a subject; and

FIGS. 12A and 12B illustrate first platen glass as viewed from above.

DETAILED DESCRIPTION

An exemplary embodiment of the disclosure will be described below withreference to the accompanying drawings.

FIG. 1 illustrates the overall configuration of an image readingapparatus 1.

The image reading apparatus 1 includes a scanner 10 and a documentfeeder 20A. The scanner 10 scans a document and generates an image ofthe document. The document feeder 20A feeds documents to the scanner 10.

The document feeder 20A includes a document stacker 21 and a dischargedsheet stacker 22. A bundle of multiple documents is placed on thedocument stacker 21. The discharged sheet stacker 22 is located underthe document stacker 21 and receives documents read by the scanner 10thereon.

The document feeder 20A also includes a feeder roller 23 and a sheetseparator 24. The feeder roller 23 feeds documents placed on thedocument stacker 21. The sheet separator 24 separate documents from eachother one by one.

On a transport path 25 through which documents are transported,transport rollers 26 and registration rollers 27 are disposed. Thetransport rollers 26 transport individual documents separated by thesheet separator 24 toward downstream rollers. The registration rollers27 supply a document while performing registration on the document to beread by the scanner 10.

On the transport path 25, a chute 28, out rollers 29, and dischargerollers 30 are also disposed. The chute 28 assists the transportation ofa document which is being read by the scanner 10. The out rollers 29transport a read document farther to the downstream side. The dischargerollers 30 discharge a document to the discharged sheet stacker 22.

The scanner 10 includes a housing 13 and an upper cover 14. First platenglass 11A and second platen glass 11B are attached to the upper cover14. On the first platen glass 11A, a document is placed manually by auser. The second platen glass 11B transmits light to read a documenttransported by the document feeder 20A.

A guide member 68 is provided between the first platen glass 11A and thesecond platen glass 11B so as to guide a document transported by thedocument feeder 20A.

A white reference plate 71, which is an example of an irradiationsubject, is provided under the guide member 68. The reference plate 71has a white surface, which serves as a reference for shading correction.Shade correction will be discussed later.

A reading unit 12 is disposed within the housing 13. The reading unit 12reads a document placed on the first platen glass 11A and a documenttransported by the document feeder 20A.

The reading unit 12 also includes a moving mechanism (not shown), whichmoves the reading unit 12 in the left-right direction in FIG. 1. Themoving mechanism is not restricted to a particular type and may beconstituted by a known mechanism.

When reading a document placed on the first platen glass 11A, thereading unit 12 shifts along under the first platen glass 11A to theright side.

When reading a document transported by the document feeder 20A, thereading unit 12 remains under the second platen glass 11B.

Inside the reading unit 12, light sources constituted by light emittingdiodes (LEDs), for example, an imaging optical system, and a sensor aredisposed. The imaging optical system condenses light reflected by adocument. The sensor receives light condensed by the imaging opticalsystem. Details of the light sources will be discussed later.

A hinge (not shown) for opening and closing the document feeder 20A isprovided on the rear side of the image reading apparatus 1. In theexemplary embodiment, a user can pivot the document feeder 20A towardthe rear side of the image reading apparatus 1.

To place a document on the first platen glass 11A, a user pivots thedocument feeder 20A toward the rear side of the image reading apparatus1.

After having placed the document on the first platen glass 11A, the userpivots the document feeder 20A toward the front side of the imagereading apparatus 1 so as to return the document feeder 20A to theoriginal position.

Then, when the user presses a start button, which is not shown, thereading of the document is started.

In the image reading apparatus 1, a controller 60 is provided to controlthe individual elements of the image reading apparatus 1.

A display 61 for displaying information is also provided in the imagereading apparatus 1. The display 61 may be constituted by a knowndisplay, such as a liquid crystal display.

FIG. 2 is a block diagram illustrating the configuration of thecontroller 60.

The controller 60 includes a control unit 101, a storage 102, and anetwork interface 103. The control unit 101 controls the operation ofthe entirety of the image reading apparatus 1. The storage 102 storesdata, for example. The network interface 103 implements communicationvia a local area network (LAN) cable.

The control unit 101 can be regarded as an information processingapparatus that processes information received from a sensor, which is alight receiver. Details of the sensor will be discussed later.

The control unit 101 includes a central processing unit (CPU) 111, aread only memory (ROM) 112, and a random access memory (RAM) 113. TheCPU 111 is an example of a processor. In the ROM 112, basic software anda basic input output system (BIOS), for example, are stored. The RAM 113is used as a work area. The control unit 101 is a computer.

The storage 102 is constituted by a semiconductor memory, for example.

The control unit 101, the storage 102, and the network interface 103 areconnected with each other via a bus 104 and a signal line, which is notshown.

A program executed by the CPU 111 may be provided to the image readingapparatus 1 as a result of being stored in a computer readable recordingmedium, such as a magnetic recording medium (magnetic tape and amagnetic disk, for example), an optical recording medium (an opticaldisc, for example), a magneto-optical recording medium, and asemiconductor memory.

A program executed by the CPU 111 may be provided to the image readingapparatus 1 via a communication medium, such as the Internet.

[Configuration of Reading Unit 12 and Other Elements]

FIG. 3 illustrates the configuration of the reading unit 12 and otherelements.

The reading unit 12 includes a light irradiator 12A, which serves aspart of a light irradiator in an exemplary embodiment of the disclosure.In the exemplary embodiment, a signal sent from the CPU 111 is inputinto the light irradiator 12A so that light can be applied to adocument.

The light irradiator 12A includes light sources. More specifically, inthe exemplary embodiment, three light sources, i.e., a first lightsource 16, a second light source 18, and a third light source 20, aredisposed.

The light irradiator 12A also includes a control unit (not shown) forcontrolling the ON/OFF operations of the first, second, and third lightsources 16, 18, and 20. The control unit may be located at any position,for example, in the body of the scanner 10.

The reading unit 12 also includes an imaging optical system 31 and asensor 32. The imaging optical system 31 condenses light reflected by adocument. The sensor 32 receives light condensed by the imaging opticalsystem 31. The reading unit 12, which is a movable unit, moves in thedirection indicated by the arrow 3A in FIG. 2.

The first platen glass 11A is constituted by a planar transparent glassplate. The first platen glass 11A is disposed along the horizontaldirection and supports a document from downward.

More specifically, the first platen glass 11A has a flat support plate11D facing upward and supports a document from downward by using thesupport plate 11D. The first platen glass 11A is not restricted to aglass plate and may be an acrylic plate.

Before the scanner 10 reads a document, the document is placed along theflat surface while being supported by the support plate 11D.

In the image reading apparatus 1 of the exemplary embodiment, not onlyregular document reading (not only obtaining color information), butalso information concerning a tilt of the surface of each portionforming a subject can be acquired. In other words, the image readingapparatus 1 of the exemplary embodiment can also be regarded as ameasurement apparatus and is able to measure a tilt of the surface ofeach portion forming a subject to be read.

Processing to be executed when obtaining information concerning a tiltof the surface of a portion forming a subject to be read will bedescribed below. Such a subject will be called a subject to be measuredor simply a subject.

A subject is not limited to a particular type. Examples of the subjectare paper, cloth, metals, resin, and rubber. The subject is notrestricted to a particular shape, either. Paper or cloth, for example,can be rolled up. A subject that can be rolled up is placed on the firstplaten glass 11A and is then disposed flat along the support plate 11D.

The first light source 16, the second light source 18, and the thirdlight source 20 are located at different positions, so that the lightirradiator 12A can apply light to a specific portion 40 of a subjectfrom multiple directions.

In the exemplary embodiment, a portion to be subjected to themeasurement of a tilt of a surface is assumed as a specific portion 40.Then, the specific portion 40 can be irradiated with light from multipledirections.

The first, second, and third light sources 16, 18, and 20 each extendalong a direction perpendicular to the plane of the drawing of FIG. 3.The first, second, and third light sources 16, 18, and 20 also extendalong a direction intersecting with (perpendicular to) the movingdirection of the reading unit 12.

In each of the first, second, and third light sources 16, 18, and 20,plural white LEDs (point light sources) are arranged in the mainscanning direction.

The first, second, and third light sources 16, 18, and 20 may beconstituted by fluorescent lamps or noble gas fluorescent lamps.

As discussed above, the imaging optical system 31 and the sensor 32 aredisposed in the reading unit 12.

The sensor 32, which is an example of the light receiver, receives lightreflected by a specific portion 40 of a subject.

The sensor 32 extends in a direction perpendicular to the plane of thedrawing of FIG. 3. In other words, the sensor 32 extends in a directionintersecting with (perpendicular to) the moving direction of the readingunit 12. The extending direction of the sensor 32 will be called themain scanning direction. The sensor 32 is a line sensor in whichlight-receiving elements 32A are aligned. Light reflected by a subjectin the main scanning direction is formed as an image on thelight-receiving elements 32A by the imaging optical system 31. In thismanner, the reading unit 12 is able to read a predetermined range of thesubject in the main scanning direction at one time.

In the exemplary embodiment, the extending direction of the first,second, and third light sources 16, 18, and 20 and the sensor 32 will becalled the main scanning direction. The direction intersecting with themain scanning direction, that is, the moving direction of the readingunit 12, will be called the sub-scanning direction.

When reading a subject, the reading unit 12 moves in the sub-scanningdirection at a predetermined speed, and more specifically, in thedirection indicated by the arrow 3A in FIG. 3.

The imaging optical system 31 is constituted by a reflecting mirror andan imaging lens, and forms an image represented by light reflected by aspecific portion 40 on the sensor 32.

Upon receiving the reflected light formed as an image by the imagingoptical system 31, the sensor 32 generates information concerning theintensity of the reflected light and outputs the generated information.

The sensor 32 is constituted by a charge-coupled device (CCD) linearimage sensor or a complementary metal oxide semiconductor (CMOS) imagesensor, for example, and outputs information concerning the intensity ofreceived light.

In the sensor 32, the multiple light-receiving elements 32A are alignedin the main scanning direction.

The sensor 32 also includes a color filter and generates an image signalindicating the color of a document or a subject. The image readingapparatus 1 of the exemplary embodiment generates three RGB values, suchas RGB (165, 42, 42), and outputs them.

In other words, in the exemplary embodiment, the image reading apparatus1 obtains color information, which is information indicating the colorof a document or a subject, and outputs the color information in apredetermined data format, more specifically, in a data formatrepresented by three values.

The first light source 16 is positioned farther upstream in the movingdirection of the reading unit 12 than a specific portion 40, and applieslight to the specific portion 40 on the downstream side.

The second and third light sources 18 and 20 are positioned fartherdownstream in the moving direction of the reading unit 12 than thespecific portion 40 and applies light to the specific portion 40 on theupstream side.

In the exemplary embodiment, the angle θ1 (angle of incidence) between aperpendicular line 70 and an optical path R1 is 45°. The perpendicularline 70 is perpendicular to the support plate 11D and passes through thespecific portion 40. The optical path R1 is a path through which lightemitted from the first light source 16 travels to the specific portion40.

In the exemplary embodiment, the angle θ2 (angle of incidence) betweenthe perpendicular line 70 and an optical path R2 is 45°. The opticalpath R2 is a path through which light emitted from the second lightsource 18 travels to the specific portion 40.

In the exemplary embodiment, the angle θ1 between the optical path R1and the perpendicular line 70 and the angle θ2 between the optical pathR2 and the perpendicular line 70 are equal to each other.

In other words, the angle θ1 between the perpendicular line 70 and theoptical path R1 through which light travels from one region at which thefirst light source 16 is located to the specific portion 40 is equal tothe angle θ2 between the perpendicular line 70 and the optical path R2through which light travels from another region at which the secondlight source 18 is located to the specific portion 40.

In the exemplary embodiment, the angle θ3 (angle of incidence) betweenthe perpendicular line 70 and an optical path R3 is 5°. The optical pathR3 is a path through which light emitted from the third light source 20travels to the specific portion 40.

Because of the provision of the second and third light sources 18 and 20in addition to the first light source 16, the light irradiator 12A isable to apply light to the specific portion 40 from differentdirections, that is, from different angles with respect to theperpendicular line 70.

The third light source 20 is located at a position which does not blocklight reflected by the specific portion 40 to travel to the sensor 32.In other words, the third light source 20 is located at a positiondisplaced from the perpendicular line 70.

More specifically, the portion corresponding to the perpendicular line70 is an optical path through which light reflected by the specificportion 40 travels to the sensor 32, and the third light source 20 islocated at a position displaced from this optical path.

The angle θ3 between the perpendicular line 70 and the optical path R3is set to be 5° in the exemplary embodiment. However, the angle θ3 maybe in a range of about 5° to 10°.

Light reflected by the specific portion 40 travels in the extendingdirection of the perpendicular line 70 and then reaches the sensor 32and is received by the sensor 32.

[Reading of Subject and Determining of Normal Angle]

Reading processing for a subject to be measured and determiningprocessing for the angle of a normal line will be described below.

In the exemplary embodiment, the CPU 111 first outputs a control signalto the light irradiator 12A, which is an example of a light irradiatorin an exemplary embodiment of the disclosure, and causes it to applylight to a specific portion 40 sequentially from multiple directions.

The CPU 111 then acquires information concerning a tilt of the surfaceof the specific portion 40, based on information on light received bythe sensor 32 when light is applied to the specific portion 40 from onedirection and information on light received by the sensor 32 when lightis applied to the specific portion 40 from another direction.

In other words, the CPU 111 acquires information concerning a tilt ofthe surface of the specific portion 40, based on information output fromthe sensor 32 when light is applied to the specific portion 40 from onedirection and information output from the sensor 32 when light isapplied to the specific portion 40 from another direction.

Irradiation of a specific portion 40 with light will be explained belowin detail.

FIGS. 4A and 4B illustrate the states of the reading unit 12 and otherelements. As shown in FIG. 4A, the CPU 111 first causes the reading unit12 to move to the right side in FIG. 4A in the state in which only thefirst light source 16 is ON. In this case, light is applied to thespecific portion 40 from the bottom left direction in FIG. 4A.

The specific portion 40 to be read by the reading unit 12 issequentially changed in accordance with the movement of the reading unit12.

In the exemplary embodiment, “specific portion 40” is a portion of asubject to be measured. More specifically, “specific portion 40” is aportion of a subject to be measured and to be read by one of themultiple receiving elements 32A aligned in the sensor 32.

As the reading unit 12 moves, the light-receiving element 32A alsomoves, and the specific portion 40 read by this light-receiving element32A is sequentially changed.

Then, as shown in FIG. 4B, the CPU 111 causes the reading unit 12 tomove to the right side in FIG. 4B in the state in which only the secondlight source 18 is ON. In this case, light is applied to the specificportion 40 from the bottom right direction in FIG. 4B.

In this manner, as a result of sequentially and separately turning ONthe first and second light sources 16 and 18, light is applied to thespecific portion 40 sequentially from multiple directions. Morespecifically, light is applied to the specific portion 40 first from thebottom left direction and then from the bottom right direction.

In the exemplary embodiment, when the reading unit 12 is moved to theright side in FIGS. 4A and 4B, the first and second light sources 16 and18 are sequentially turned ON.

Alternatively, the first light source 16 may be turned ON when thereading unit 12 is moved to the right side in FIGS. 4A and 4B, and thesecond light source 18 may be turned ON when the reading unit 12 ismoved to the left side in FIGS. 4A and 4B.

The order in which the first and second light sources 16 and 18 areturned ON is not restricted to that described above. The second lightsource 18 may be turned ON first, and then, the first light source 16may be turned ON.

The CPU 111 obtains information on light received by the sensor 32 whenlight is applied to the specific portion 40 from the bottom leftdirection. The CPU 111 also obtains information on light received by thesensor 32 when light is applied to the specific portion 40 from thebottom right direction.

In other words, the CPU 111 obtains a value output from the sensor 32when light is applied to the specific portion 40 from the bottom leftdirection. The CPU 111 also obtains a value output from the sensor 32when light is applied to the specific portion 40 from the bottom rightdirection.

The CPU 111 then acquires information concerning a tilt of the surfaceof the specific portion 40, based on the information on light receivedby the sensor 32 (output value from the sensor 32) when light is appliedto the specific portion 40 from the bottom left direction and theinformation on light received by the sensor 32 (output value from thesensor 32) when light is applied to the specific portion 40 from thebottom right direction.

More specifically, if the value represented by the information on lightreceived by the sensor 32 when light is applied to the specific portion40 from the bottom left direction (hereinafter such information will becalled first information) is equal to the value represented by theinformation on light received by the sensor 32 when light is applied tothe specific portion 40 from the bottom right direction (hereinaftersuch information will be called second information), the CPU 111determines that a tilt of the surface of the specific portion 40 is 0°.

A perpendicular line 70, which is perpendicular to the support plate 11Dand passes through the specific portion 40, is set, as shown in FIG. 4A.

When the first information and the second information are equal to eachother, the CPU 111 outputs information indicating that a tilt of anormal line 40X, which is normal to a surface 40A of the specificportion 40, that is, a tilt of the normal line 40A with respect to theperpendicular line 70, is 0°.

When the first information and the second information are different fromeach other, the CPU 111 outputs information indicating that a tilt ofthe normal line 40X with respect to the perpendicular line 70 is a valueother than 0°.

If the value represented by the first information is greater than thatby the second information, the normal line 40X tilts in the directionindicated by the arrow 4E in FIG. 4A.

In this case, the CPU 111 determines the specific angle of the normalline 40X with respect to the perpendicular line 70 (hereinafter such anangle will be called the normal angle), based on the value representedby the first information and that by the second information. Details ofdetermining of the normal angle will be discussed later.

If the value represented by the first information is smaller than thatby the second information, the normal line 40X tilts in the directionindicated by the arrow 4F in FIG. 4A.

In this case, the CPU 111 determines the specific angle of the normalline 40X with respect to the perpendicular line 70 (normal angle), basedon the value represented by the first information and that by the secondinformation. Details of determining of the normal angle will bediscussed later.

[Details of Processing]

Processing to be executed from when light is applied to a specificportion 40 until when the normal angle is determined will be describedin detail.

In the exemplary embodiment, shading correction is first performed forthe first and second light sources 16 and 18. Details of shadingcorrection will be discussed later.

Then, the first and second light sources 16 and 18 are individuallyturned ON so as to obtain two scan images.

More specifically, as discussed above, as a result of moving the readingunit 12 in the state in which the first light source 16 is ON andapplying light to each specific portion 40 from the bottom leftdirection, the first scan image is obtained.

Then, as a result of moving the reading unit 12 in the state in whichthe second light source 18 is ON and applying light to each specificportion 40 from the bottom right direction, the second scan image isobtained.

Thereafter, the two scan images are formed into grayscale images.

Then, two pixel values of the same pixel of the two scan images areextracted. In other words, two pixel values are extracted from the samespecific portion 40.

More specifically, the value output from the sensor 32 when light isapplied from the first light source 16 to a specific portion 40 and thevalue output from the sensor 32 when light is applied from the secondlight source 18 to this specific portion 40 are obtained.

In the exemplary embodiment, a specific portion 40 is read by onelight-receiving element 32A, as stated above.

Two output values, that is, the value output from this light-receivingelement 32A when light is applied from the first light source 16 to thespecific portion 40 and the value output from this light-receivingelement 32A when light is applied from the second light source 18 to thespecific portion 40 are obtained.

More specifically, the pixel value of the same pixel position (x, y) isextracted from each of the scan images.

The pixel value extracted from one scan image is set to be D_−45(x, y),while that from the other scan image is set to be D_45(x, y).

The numerical value “−45” indicates the angle of incidence of lightemitted from the first light source 16, while the numerical value “45”indicates the angle of incidence of light emitted from the second lightsource 18.

Then, the pixel value (D_−45) obtained when light is applied from thefirst light source 16 is associated with the angle of incidence “−45°”,while the pixel value (D_45) obtained when light is applied from thesecond light source 18 is associated with the angle of incidence “+45°”.

When the angle of incidence with respect to the perpendicular line 70 is±180°, the value output from the sensor 32 is zero. Accordingly, thepixel value “0” and the angle of incidence “−180°” are associated witheach other, while the pixel value “0” and the angle of incidence “+180°”are associated with each other.

The CPU 111 then conducts fitting by using the angle of incidence as anindependent variable (−180° to +180°, for example) and the pixel valueas a dependent variable (0 to 255, for example).

More specifically, based on the four angles of incidence, −180°, −45°,+45°, and +180°, and the four associated pixel values, the CPU 111conducts fitting by using the bidirectional reflectance distributionfunction (BRDF) model (Cook-Torrance) or spline interpolation.

For example, the CPU 111 executes fitting processing for fitting aspline curve to the above-described pixel values.

The CPU 111 then extracts the peak from the spline curve and assumes theindependent variable (angle of incidence) corresponding to this peak asthe angle of incidence for the surface 40A of a subject specific portion40.

Based on this angle of incidence, the CPU 111 determines the normalangle of the surface 40A of the specific portion 40.

The CPU 111 executes the above-described fitting processing for allspecific portions 40 to determine the normal angle of each specificportion 40.

FIG. 5 illustrates the relationship between the angle of incidence andthe normal angle.

In FIG. 5, a represents an example of the angle of incidence determinedbased on the peak of the spline curve subjected to fitting processing.More specifically, in FIG. 5, the angle of incidence a is 30°.

The CPU 111 sets half the value of this angle of incidence a to be thenormal angle β of the surface 40A of the specific portion 40. In thisexample, the CPU 111 determines that the normal angle β is 15°.

FIG. 6 illustrates a range 32′ of a subject that can be read by thesensor 32 at one time, the first and second light sources 16 and 18, anda specific portion 40 of a subject, as viewed from the directionindicated by the arrow VI in FIG. 3.

As described above, as a result of sequentially applying light from thefirst and second light sources 16 and 18, the specific portion 40 can beirradiated with light from multiple regions of the light sourcespositioned around the perpendicular line 70.

More specifically, light is applied to the specific portion 40sequentially from a first region 6A and a second region 6B, for example.

The perpendicular line 70 is taken as a reference. The orientation inwhich the first region 6A is seen from the perpendicular line 70 isdifferent from that in which the second region 6B is seen from theperpendicular line 70.

Light is applied to the specific portion 40 from multiple regions, andthe orientation in which one region is seen from the perpendicular line70 and that in which another region is seen from the perpendicular line70 are different from each other.

In this manner, light is applied to the specific portion 40 sequentiallyfrom these multiple regions located in different orientations.

When the first and second light sources 16 and 18 are sequentiallyturned ON, light is applied to the specific portion 40 sequentially fromthe first region 6A and the second region 6B.

The angle between the orientation in which the first region 6A is seenfrom the perpendicular line 70 and that in which the second region 6B isseen from the perpendicular line 70 is 180°. Light is applied to thespecific portion 40 sequentially from these first and second regions 6Aand 6B.

More specifically, the CPU 111 controls ON/OFF operations of the firstand second light sources 16 and 18 so that light is applied to thespecific portion 40 sequentially from the first and second regions 6Aand 6B between which the above-described angle is 180°.

In this manner, by applying light to the specific portion 40sequentially from two regions between which the above-described angle is180°, a tilt (normal angle) of the surface 40A of the specific portion40 can be determined with high accuracy.

More specifically, as shown in FIG. 11, when each of the first andsecond light sources 16 and 18 is turned ON, it is ON in the entirety ofthe main scanning direction. In the exemplary embodiment, when each ofthe first and second light sources 16 and 18 is ON, an image constitutedby pixels for one line in the main scanning direction is read. As aresult of the CPU 111 controlling the ON/OFF operations of the first andsecond light sources 16 and 18, light is applied to each specificportion 40 sequentially from the corresponding first and second regions6A and 6B located at both sides of the specific portion 40 and formingthe above-described angle of 180°.

It is now assumed that light is applied to a specific portion 40 onlyfrom one region of a light source to determine a tilt of the surface 40Aof the specific portion 40.

In this case, light reflected by the specific portion 40 is received,and a tilt of the surface 40A of the specific portion 40 can still bedetermined from the intensity of the reflected light.

The intensity of light reflected by a specific portion 40 is susceptibleto the color of the specific portion 40. That is, the intensity ofreflected light varies in accordance with the color of the specificportion 40. This may fail to accurately determine a tilt of the surface40A of the specific portion 40.

In contrast, if light is applied to a specific portion 40 sequentiallyfrom two regions, as in the exemplary embodiment, the intensity of lightis less susceptible to the color of the specific portion 40, therebymaking it possible to measure a tilt of the surface 40A of the specificportion 40 more accurately.

As shown in FIG. 6, a plane 90 perpendicular to the support plate 11Dand parallel with the main scanning direction and passing through thespecific portion 40 is set.

In the exemplary embodiment, light sources (first and second lightsources 16 and 18) are respectively disposed in first and second areasAR1 and AR2 located at both sides of the plane 90.

The specific portion 40 is irradiated with light sequentially from thefirst and second areas AR1 and AR2. This type of light irradiation canreduce the influence of the color of the specific portion 40 andaccordingly determine a tilt of the surface 40A of the specific portion40 with higher accuracy.

In the above-described example, the angle between the orientation of thefirst region 6A and that of the second region 6B is 180°. However, thisangle is not restricted to 180° and may be any value greater than 90°.

In other words, a specific portion 40 may be irradiated with light fromtwo regions between which the above-described angle is greater than 90°and smaller than 180°.

In the image reading apparatus 1 of the exemplary embodiment, because ofits configuration, a specific portion 40 is irradiated with light fromtwo regions between which the above-described angle is 180°.Alternatively, point light sources may be used and be moved with respectto the normal line. In this case, light can be applied, not only fromtwo regions between which the above-described angle is 180°, but alsofrom any of two regions between which the angle is smaller than 180°.

If the angle between the orientations of two regions is smaller than90°, a specific portion 40 is irradiated with light from the same sidewith respect to the normal line. This is likely to decrease the accuracyin determining a tilt of the surface 40A of the specific portion 40. Incontrast, if the angle between the orientations of two regions is largerthan 90°, the accuracy in determining a tilt of the surface 40A isenhanced.

The CPU 111 may cause the light irradiator 12A (see FIG. 3) to turn ON apart of a light source disposed linearly and then to turn ON anotherpart of the light source so as to apply light to a specific portion 40sequentially from multiple directions.

A specific example of this type of light irradiation will be discussedbelow.

The first light source 16 is disposed along the main scanning direction.FIG. 7A illustrates the sensor 32 and the first and second light sources16 and 18, as viewed from the direction indicated by the arrow VII inFIG. 3. As shown in FIG. 7A, one part of the first light source 16 inits longitudinal direction may be turned ON, and then, another part ofthe first light source 16 in its longitudinal direction may be turnedON, as shown in FIG. 7B, thereby irradiating the specific portion 40with light sequentially from multiple directions.

In the example in FIGS. 7A and 7B, one part of the first light source 16in its longitudinal direction is turned ON, and then, another part ofthe first light source 16 separated from the previous part with a gaptherebetween is turned ON, thereby applying light to the specificportion 40 sequentially from multiple directions.

More specifically, as shown in FIG. 7A, one end portion 16A of the firstlight source 16 in its longitudinal direction is turned ON, and then,the other end portion 16B of the first light source 16 is turned ON, asshown in FIG. 7B, thereby applying light to the specific portion 40sequentially from multiple directions.

As a result of sequentially turning ON one part of the light source 16in its longitudinal direction and then another part so as to sandwichthe specific portion 40 between these two parts, light can be applied tothe specific portion 40 from different directions.

That is, the specific portion 40 can be irradiated with light from oneside in the main scanning direction and then from the other side.

When sequentially turning ON different parts of the first light source16 in this manner, it is preferable that the second light source 18 bealso turned ON. This enhances the accuracy in determining the normalangle.

If the first light source 16 is only turned ON, a shade extending in thesub-scanning direction may appear in a specific portion 40, which maydecrease the accuracy in determining the normal angle.

Turning ON the second light source 18 together with the first lightsource 16 makes it less likely to cause this type of shade, therebymaintaining the accuracy in determining the normal angle.

When the second light source 18 is turned ON together with the firstlight source 16, the same position of the second light source 18 as thatof the first light source 16 in the main scanning direction is turnedON.

For example, when the end portion 16A of the first light source 16 inits longitudinal direction is turned ON, an end portion 18A (see FIG.7A) of the second light source 18 in its longitudinal direction isturned ON. When the other end portion 16B of the first light source 16in its longitudinal direction is turned ON, the other end portion 18B(see FIG. 7B) of the second light source 18 in its the longitudinaldirection is turned ON.

Concerning the normal angle of the surface 40A of a specific portion 40,a component in the sub-scanning direction can be obtained as a result ofexecuting processing in FIG. 6, while a component in the main scanningdirection can be obtained as a result of executing processing in FIGS.7A and 7B.

In the exemplary embodiment, as a result of executing processing shownin FIGS. 7A and 7B as well as that in FIG. 6, a component in thesub-scanning direction and a component in the main scanning directionconcerning the normal angle can be obtained without the need to changethe orientation of a subject to be measured.

Alternatively, the CPU 111 may instruct a user to rotate a subject.

More specifically, the CPU 111 may instruct a user to rotate a subjectaround the perpendicular line 70 with respect to the support plate 11D(see FIG. 3).

In the exemplary embodiment, when the scanner 10 reads a subject, thissubject is placed on the flat support plate 11D of the first platenglass 11A (see FIG. 3).

The CPU 111 instructs a user to rotate the subject around theperpendicular line 70 with respect to the support plate 11D. Morespecifically, the CPU 111 instructs the user to rotate the subject by90°, for example, around the perpendicular line 70.

FIG. 8 illustrates a subject as viewed from the direction indicated bythe arrow VIII in FIG. 3.

The perpendicular line 70 perpendicular to the support plate 11D isindicated by the arrow 8A in FIG. 8. The CPU 111 instructs a user torotate the subject by 90°, for example, around the perpendicular line70.

For example, the CPU 111 displays a message “Please rotate the subjectby 90°” on the display 61 (see FIG. 1).

After the user has rotated the subject, the CPU 111 moves the readingunit 12 in the state in which the first light source 16 is ON and thenmoves the reading unit 12 in the state in which the second light source18 is ON, as described above.

FIGS. 12A and 12B illustrate the first platen glass 11A as viewed fromabove. As shown in FIGS. 12A and 12B, a rectangular subject is placed onthe first platen glass 11A with its corner adjusted to the top left ofthe first platen glass 11A. When the user has rotated the subject, thestate of the subject is changed from that in FIG. 12A to that in FIG.12B. Then, the CPU 111 moves the reading unit 12 in the state in whichthe first light source 16 is ON, and then moves the reading unit 12 inthe state in which the second light source 18 is ON.

As a result, regarding the normal angle of the surface 40A of thespecific portion 40, a component in the direction along the long sidesof the rectangular subject and a component in the direction along theshort sides are determined.

One approach to determining a component of the normal angle of thesurface 40A of the specific portion 40 in the main scanning direction isto turn ON multiple parts of the first light source 16, as stated above.

Another approach is to rotate a subject as discussed above. If thisapproach is employed, an image, which serves as a positional reference,is provided to a subject in advance, and, based on this image, acomponent in the sub-scanning direction and a component in the mainscanning direction for each specific portion 40 are determined.

Additionally, the scanner 10 may judge whether the subject has beenrotated by 90°, and if the subject has not been rotated by 90°, aninstruction to displace the subject may be provided via the display 61.

A judgement as to whether the subject has been rotated by 90° may bemade in accordance with whether the corresponding side of the rotatedsubject is disposed along the main scanning direction or thesub-scanning direction.

If the corresponding side of the rotated subject is disposed along themain scanning direction or the sub-scanning direction, it is judged thatthe subject has been rotated by 90°.

If the corresponding side of the rotated subject is not disposed alongthe main scanning direction or the sub-scanning direction, it is judgedthat the subject has not been rotated by 90°. In this case, a messageinstructing a user to displace the subject is provided via the display61.

The third light source 20 may also be used to apply light to a specificportion 40. More specifically, the CPU 111 may move the reading unit 12in the state in which only the third light source 20 is ON and receivelight reflected by the specific portion 40.

In this case, light is applied to the specific portion 40 sequentiallyfrom multiple directions whose angles with respect to the perpendicularline 70 are different from each other.

More specifically, in addition to the second light source 18, the thirdlight source 20 is also turned ON, so that the specific portion 40 canbe irradiated with light sequentially from different directions.

As shown in FIG. 3, the angle θ2 between the perpendicular line 70 andthe optical path R2 through which light travels from the second lightsource 18 to the specific portion 40 is different from the angle θ3between the perpendicular line 70 and the optical path R3 through whichlight travels from the third light source 20 to the specific portion 40.

As a result of sequentially turning ON the second and third lightsources 18 and 20, light is applied to the specific portion 40sequentially from multiple directions whose angles with respect to theperpendicular line 70 are different from each other.

In other words, as a result of sequentially turning ON the second andthird light sources 18 and 20, the specific portion 40 is irradiatedwith light sequentially from a region where the second light source 18is located and another region where the third light source 20 islocated.

The specific portion 40 is thus irradiated with light sequentially fromdifferent directions.

FIG. 9 illustrates the first, second, and third light sources 16, 18,and 20 and the sensor 32 as viewed from the direction indicated by thearrow IX in FIG. 3.

Focusing on a point light source 9A (hereinafter called a first pointlight source 9A) and a point light source 9B (hereinafter called asecond point light source 9B) in FIG. 9, the angle between theorientation in which the first point light source 9A is seen from theperpendicular line 70 and that in which the second point light source 9Bis seen from the perpendicular line 70 is smaller than 90°.

More specifically, the orientation in which the first point light source9A is seen from the perpendicular line 70 and that in which the secondpoint light source 9B is seen from the perpendicular line 70 are alignedwith each other, and the angle between the two orientations isaccordingly 0°, which is smaller than 90°.

In the exemplary embodiment, when the second and third light sources 18and 20 are sequentially turned ON, light is applied to a specificportion 40 sequentially from the first point light source 9A and thesecond point light source 9B.

In this case, the specific portion 40 is irradiated with lightsequentially from two point light sources (two regions) in which theangle between the orientation of one point light source with respect tothe perpendicular line 70 and that of the other point light source withrespect to the perpendicular line 70 is 0°.

In the exemplary embodiment, as a result of turning ON the third lightsource 20 in addition to the first and second light sources 16 and 18,light is applied to a specific portion 40 from three different lightsources (first, second, and third light sources 16, 18, and 20) disposedat different positions. This further improves the accuracy indetermining the normal angle, compared with when light is applied onlyfrom two light sources.

More specifically, when the third light source 20 is also turned ON, theabove-described fitting can be conducted based on five pixel valuescorresponding to five angles of incidence, thereby further enhancing theaccuracy in determining the normal angle.

In the above-described example, fitting is executed based on the fourpixel values corresponding to the four angles of incidence (−180°, −45°,+45°, +180°).

In contrast, when the third light source 20 is also turned ON, fittingis executed based on five pixel values corresponding to five angles ofincidence (−180°, −45°, +45°, +180°, +5°), thereby further enhancing theaccuracy in determining the normal angle.

For example, if a specific portion 40 has a sharp unevenness or isconsiderably black, two pixel values corresponding to two angles ofincidence (−45°, +45°) may become similar to each other. In this case,the peak of a spline curve subjected to fitting may not appeardistinctively.

In contrast, if the third light source 20 is turned ON, as in theexemplary embodiment, the peak of a spline curve is likely to appeardistinctively, thereby enhancing the accuracy in determining the normalangle.

[Shading Correction]

Shading correction will be discussed.

In the exemplary embodiment, the white reference plate (see FIG. 1) isprovided, as stated above.

To perform shading correction, light is applied from each of the firstand second light sources 16 and 18 to the white reference plate 71,which serve as a common irradiation subject.

More specifically, to determine the normal angle, shading correction isfirst conducted for the first and second light sources 16 and 18. Lightis first applied to the white reference plate 71 sequentially from thefirst and second light sources 16 and 18 in the state in which thereading unit 12 is placed under the white reference plate 71.

In the exemplary embodiment, the CPU 111 obtains information on lightreceived by the sensor 32 when light is applied from the first lightsource 16 to the reference plate 71 (such information will be calledfirst light information) and information on light received by the sensor32 when light is applied from the second light source 18 to thereference plate 71 (such information will be called second lightinformation).

The CPU 111 then generates two items of correction information, based onthe first light information and the second light information.

More specifically, based on the first light information and the secondlight information, the CPU 111 generates first correction informationused for correcting information on light received by the sensor 32 whenlight is applied from the first light source 16 to a specific portion40, and also generates second correction information used for correctinginformation on light received by the sensor 32 when light is appliedfrom the second light source 18 to the specific portion 40.

This makes it less likely to vary output values from the sensor 32 dueto the difference in the light sources.

There may be nonuniformities in the amount of light emitted from each ofthe first and second light sources 16 and 18. In this case, even if thenormal angle of a specific portion 40 is 0°, in other words, even if thesame specific portion 40 is read under the same condition, the outputvalue from the sensor 32 when light is applied from the first lightsource 16 to the specific portion 40 and that when light is applied fromthe second light source 18 to the specific portion 40 may becomedifferent from each other.

In the exemplary embodiment, the above-described two items of correctioninformation, i.e., the first correction information and the secondcorrection information, are generated so that information on lightreceived by the sensor 32 when light is applied from the first lightsource 16 to the common reference plate 71 (the normal angle is 0°) andinformation on light received by the sensor 32 when light is appliedfrom the second light source 18 to the common reference plate 71 becomeequal to each other.

More specifically, the first correction information and the secondcorrection information are generated for each of the multiplelight-receiving elements 32A provided in the sensor 32.

Then, every time the sensor 32 receives light reflected by a specificportion 40 irradiated with light, the output value from eachlight-receiving element 32A is corrected by using one of the firstcorrection information and the second correction information.

More specifically, when the sensor 32 has received light reflected by aspecific portion 40 irradiated with light emitted from the first lightsource 16, the CPU 111 corrects the output value from eachlight-receiving element 32A by using the first correction information.

When the sensor 32 has received light reflected by a specific portion 40irradiated with light emitted from the second light source 18, the CPU111 corrects the output value from each light-receiving element 32A byusing the second correction information.

This makes it less likely to decrease the accuracy in determining thenormal angle due to the difference in the light sources.

In the above-described example, shading correction is performed for thefirst and second light sources 16 and 18. Shading correction is alsoconducted for the third light source 20 in a similar manner.

More specifically, the CPU 111 generates correction information so thatinformation on light received by the sensor 32 when light is appliedfrom the first light source 16 to the reference plate 71 and that whenlight is applied from the third light source 20 to the reference plate71 become equal to each other.

[Outputting of Tilt Information]

In the exemplary embodiment, as stated above, the image readingapparatus 1 obtains color information concerning the color of a subjectand outputs the color information in a predetermined data format.

The CPU 111 obtains information concerning a tilt (normal angle) of thesurface 40A of a specific portion 40 and outputs this information(hereinafter called tilt information) in a predetermined data format ofthe same type as that for outputting the color information.

In the exemplary embodiment, color information is output in a dataformat of three consecutive RGB values. Tilt information is also outputin a data format of three consecutive values.

More specifically, tilt information is output in a data format of threeconsecutive XYZ values. The X value represents an X component, which isa component of the normal angle in the sub-scanning direction. The Yvalue represents a Y component, which is a component of the normal anglein the main scanning direction. The Z value represents a Z component,which is a component of the normal angle in a direction perpendicular tothe main scanning direction and the sub-scanning direction.

As a result of outputting tilt information in a data format of the sametype as that for outputting color information in this manner, a computerwhich receives this tilt information is able to display the amount oftilt of each specific portion 40 by using different colors without usingspecial software.

In other words, by using software for displaying the color of each pixelbased on the RGB values, the computer is able to display the amount oftilt of each specific portion 40 by using colors.

To output tilt information in a data format of the same type as that foroutputting color information, the CPU 111 first determines a tangentvector Nx=(1, 0, X′) in the sub-scanning direction from the normal angleconcerning the sub-scanning direction. The CPU 111 also determines atangent vector Ny=(0, 1, Y′) in the main scanning direction from thenormal angle concerning the main scanning direction.

The CPU 111 then find the cross product of these two tangent vectors Nxand Ny so as to determine the three-dimensional normal vector N. Then,the CPU 111 calculates the norm of the three-dimensional normal vector Nand normalizes the three-dimensional normal vector N (n=N/|N|).

The CPU 111 then adds one to each component of n, divides the resultingvalue by two, and multiplies the resulting value by 255, therebydetermining the value corresponding to each of the XYZ components.

The CPU 111 then outputs the three values corresponding to the XYZcomponents in the above-described data format.

[Obtaining of Color Information]

In the above-described example, processing for obtaining tiltinformation has principally been discussed. In this processing, colorinformation is first removed by forming a color image into a grayscaleimage as discussed above, and then, tilt information is obtained fromthe grayscale image.

To obtain color information about a subject, the subject is read bymoving the reading unit 12 in the state in which the first and secondlight sources 16 and 18 are both ON.

That is, to obtain color information about the subject, the subject isscanned by both turning ON the first and second light sources 16 and 18,separately from scanning for obtaining tilt information.

Scanning a subject by both turning ON the first and second light sources16 and 18 makes it less likely to cause a shade in the subject, therebymaintaining the precision in reading the subject.

The order of the execution of scanning for obtaining color informationand scanning for obtaining tilt information is not restricted, andeither scanning may be performed first.

[Others]

In the above-described example, two light sources, i.e., the first andsecond light sources 16 and 18, are used, and by sequentially andseparately turning ON the first and second light sources 16 and 18,light is applied to a specific portion 40 from multiple directions.

However, the provision of multiple light sources is not inevitable. FIG.10 illustrates another example of the configuration of the reading unit12. As shown in FIG. 10, even with one light source, a specific portion40 can be irradiated with light from multiple directions.

In the reading unit 12 configured as shown in FIG. 10, a light source180 is disposed in the region on the right side of the plane 90.

In the region on the left side of the plane 90, a light reflector 181,such as a mirror which reflects light from the light source 180 towardthe specific portion 40, is disposed.

A light blocking member 182 is also provided to block light emitted fromthe light source 180.

The light blocking member 182 is movable and shifts to a first opticalpath R11 heading from the light source 180 to the specific portion 40and to a second optical path R12 heading from the light source 180 tothe light reflector 181.

In the above-described configuration, to apply light to the specificportion 40 from the bottom left direction, the light blocking member 182is located on the first optical path R11 so as to apply light from thelight reflector 181.

To apply light to the specific portion 40 from the bottom rightdirection, the light blocking member 182 is located on the secondoptical path R12 so as to apply light from the light source 180.

In the embodiment above, the term “processor” refers to hardware in abroad sense. Examples of the processor include general processors (e.g.,CPU: Central Processing Unit), and dedicated processors (e.g., GPU:Graphics Processing Unit, ASIC: Application Integrated Circuit, FPGA:Field Programmable Gate Array, and programmable logic device).

In the embodiment above, the term “processor” is broad enough toencompass one processor or plural processors in collaboration which arelocated physically apart from each other but may work cooperatively. Theorder of operations of the processor is not limited to one described inthe embodiment above, and may be changed.

The foregoing description of the exemplary embodiment of the presentdisclosure has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit thedisclosure to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and its practical applications, therebyenabling others skilled in the art to understand the disclosure forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of thedisclosure be defined by the following claims and their equivalents.

What is claimed is:
 1. A measurement apparatus comprising: a lightirradiator that is able to apply light from a plurality of directions toa specific portion of a subject to be measured; a light receiver thatreceives light reflected by the specific portion; and a processorconfigured to cause the light irradiator to apply light to the specificportion sequentially from the plurality of directions, and acquireinformation concerning a tilt of a surface of the specific portion,based on information on light received by the light receiver when lightis applied to the specific portion from a first direction andinformation on light received by the light receiver when light isapplied to the specific portion from a second direction, the pluralityof directions including the first and second directions.
 2. Themeasurement apparatus according to claim 1, further comprising: asupport plate that supports the subject, wherein the light irradiator isable to apply light to the specific portion from each of a plurality ofregions located around a perpendicular line, the perpendicular linebeing perpendicular to the support plate and passing through thespecific portion, an orientation in which each of the plurality ofregions is seen from the perpendicular line being different from anorientation in which another one of the plurality of regions is seenfrom the perpendicular line, and the processor is configured to causethe light irradiator to apply light to the specific portion sequentiallyfrom the plurality of regions.
 3. The measurement apparatus according toclaim 2, wherein: the light irradiator is able to apply light to thespecific portion from a first region and a second region of theplurality of regions, an angle between the orientation in which thefirst region is seen from the perpendicular line and the orientation inwhich the second region is seen from the perpendicular line beinggreater than 90°; and the processor is configured to cause the lightirradiator to apply light to the specific portion sequentially from atleast the first region and the second region.
 4. The measurementapparatus according to claim 2, wherein: the light irradiator is able toapply light to the specific portion from a first region and a secondregion of the plurality of regions, an angle between the orientation inwhich the first region is seen from the perpendicular line and theorientation in which the second region is seen from the perpendicularline being 180°; and the processor is configured to cause the lightirradiator to apply light to the specific portion sequentially from atleast the first region and the second region.
 5. The measurementapparatus according to claim 3, wherein an angle between theperpendicular line and an optical path through which light travels fromthe first region to the specific portion and an angle between theperpendicular line and an optical path through which light travels fromthe second region to the specific portion are equal to each other. 6.The measurement apparatus according to claim 4, wherein an angle betweenthe perpendicular line and an optical path through which light travelsfrom the first region to the specific portion and an angle between theperpendicular line and an optical path through which light travels fromthe second region to the specific portion are equal to each other. 7.The measurement apparatus according to claim 1, wherein: the lightirradiator includes a plurality of light sources disposed at differentpositions; and the processor is configured to cause the light irradiatorto sequentially and separately turn ON the plurality of light sourcesand to apply light to the specific portion sequentially from theplurality of directions.
 8. The measurement apparatus according to claim1, wherein: the light irradiator includes a light source disposedlinearly; and the processor is configured to cause the light irradiatorto turn ON a part of the light source and then to turn ON another partof the light source and to apply light to the specific portionsequentially from the plurality of directions.
 9. The measurementapparatus according to claim 8, wherein the processor is configured tocause the light irradiator to turn ON one end portion of the lightsource in its longitudinal direction and then to turn ON the other endportion of the light source in its longitudinal direction and to applylight to the specific portion sequentially from the plurality ofdirections.
 10. The measurement apparatus according to claim 1, furthercomprising: a support plate that supports the subject, wherein theplurality of directions are directions whose angles with respect to aperpendicular line are different from each other, the perpendicular linebeing perpendicular to the support plate and passing through thespecific portion.
 11. The measurement apparatus according to claim 10,wherein: the light irradiator applies light sequentially from at leasttwo first and second regions so as to apply light to the specificportion from the plurality of directions; the processor causes the lightirradiator to apply light to the specific portion sequentially from atleast the two first and second regions; and an angle between anorientation in which the first region is seen from the perpendicularline and an orientation in which the second region is seen from theperpendicular line is smaller than 90°.
 12. The measurement apparatusaccording to claim 1, further comprising: a support plate that supportsthe subject, wherein the processor is configured to instruct a user torotate the subject around a perpendicular line which is perpendicular tothe support plate.
 13. The measurement apparatus according to claim 12,wherein the processor is configured to instruct the user to rotate thesubject around the perpendicular line by 90°.
 14. The measurementapparatus according to claim 1, wherein: the light irradiator includesfirst and second light sources, the first light source being used forapplying light to the specific portion from the first direction, thesecond light source being used for applying light to the specificportion from the second direction; and based on information on lightreceived by the light receiver when light is applied from the firstlight source to a common irradiation subject and information on lightreceived by the light receiver when light is applied from the secondlight source to the common irradiation subject, the processor isconfigured to generate correction information used for correctinginformation on light received by the light receiver when light isapplied from the first light source to the specific portion and alsogenerate correction information used for correcting information on lightreceived by the light receiver when light is applied from the secondlight source to the specific portion.
 15. The measurement apparatusaccording to claim 1, wherein: color information concerning a color of asubject to be measured by the measurement apparatus is output from themeasurement apparatus in a predetermined format; and the processor isconfigured to output tilt information in a predetermined format of thesame type as the predetermined format used for outputting the colorinformation, the tilt information being the information concerning thetilt of the surface of the specific portion.
 16. A non-transitorycomputer readable medium storing a program causing a computer to executea process, the process comprising: causing a light irradiator to applylight sequentially from a plurality of directions to a specific portionof a subject to be measured; and acquiring information concerning a tiltof a surface of the specific portion, based on information on lightreceived by a light receiver when light is applied to the specificportion from a first direction and information on light received by thelight receiver when light is applied to the specific portion from asecond direction, the plurality of directions including the first andsecond directions.
 17. An information processing apparatus comprising: aprocessor configured to process information output from a light receiverwhich receives light reflected by a specific portion of a subject to bemeasured, wherein the processor is configured to obtain firstinformation, the first information being information on light receivedby the light receiver when light is applied to the specific portion froma first direction, obtain second information, the second informationbeing information on light received by the light receiver when light isapplied to the specific portion from a second direction, and acquireinformation concerning a tilt of a surface of the specific portion,based on the first information and the second information.
 18. Theinformation processing apparatus according to claim 17, wherein theprocessor is configured to obtain information concerning intensity oflight received by the light receiver as each of the first informationand the second information, and acquire the information concerning thetilt of the surface of the specific portion, based on the informationconcerning the intensity of light obtained as the first information andthe information concerning the intensity of light obtained as the secondinformation.